Isolation of Microparticles from Soils and Road Dust to Determine Their Elemental Composition

In this paper, we propose a method for isolating PM1 and PM10 microparticles from soil and road dust samples using centrifugation. The dispersion of soils and dust was carried out by ultrasonic dispersion at a sound wave power of 30 kHz. A laboratory experiment was conducted to test the technique by isolating PM1 microparticles from the background sandy loamy umbric horizon of Retisol and the polluted surface horizon of Urban Technosol within the southern taiga; the clay loamy chernic horizon of Calcaric Chernic Phaeozem and road dust within the steppe zone with transitions to forest-steppe landscapes. This was achieved through decantation and by varying the speeds and times of centrifugation. The particle size distribution and elemental compositions of the isolated microparticles were analyzed using laser diffraction particle sizer, inductively coupled plasma atomic emission spectrometry (ICP-AES), and mass spectrometry (ICP-MS), respectively. The median size of the microparticles isolated using the recommended centrifugation parameters (1100 rpm for 8 min) was found to be 3 µm for the umbric horizon of Retisol, 1 µm for the surface horizon of urban soil, and 0.8 µm for the chernic horizon of Calcaric Chernic Phaeozem and road dust. The study’s results demonstrated the potential of the proposed fractionation technique for extracting PM1 and PM10 microparticles from soils, road dust, and other environmental compartments. Increasing the number of rotations and the duration of centrifugation beyond the standard parameters leads to an overestimation of the concentrations of many elements in all four samples due to the deposition of particles of 1 μm or more in size.